Add missing 'root' attribute to vfs policies

The commit "os: avoid using deprecated APIs" tightens the policy
configuration of the VFS server such that the 'root' attribute is no
longer optional.

repos/libports/recipes/pkg/test-sequence/runtime

@@ -43,7 +43,7 @@
 			<provides> <service name="File_system"/> </provides>
 			<config>
 				<vfs> <log/> </vfs>
-				<default-policy writeable="yes"/>
+				<default-policy root="/" writeable="yes"/>
 			</config>
 		</start>
 		<start name="log_2" caps="64">

repos/os/recipes/pkg/test-fs_log/runtime

@@ -39,7 +39,7 @@
 					<log name="bomb-master.log"/>
 					<dir name="bomb-master"> <log name="bomb_g5.log"/> </dir>
 				</vfs>
-				<policy label_prefix="fs_log" writeable="yes"/>
+				<policy label_prefix="fs_log" writeable="yes" root="/"/>
 			</config>
 		</start>
 		<start name="fs_log">

repos/os/run/log_core.run

@@ -53,7 +53,7 @@ append config {
 				<!-- be careful to avoid endless output loop for core.log -->
 				<dir name="log_core"> <} [log_service] { name="log.log"/> </dir>
 			</vfs>
-			<policy label_prefix="fs_log" writeable="yes"/>
+			<policy label_prefix="fs_log" writeable="yes" root="/"/>
 		</config>
 	</start>